Field of the Invention
The present invention relates to an image pickup device including an asymmetrical microlens, and to an image pickup system.
Description of the Related Art
Japanese Patent Laid-Open Nos. 2009-109965 and 2009-290157 each describe an image pickup device in which image pickup pixels, and focus detection pixels capable of phase difference detection, are provided in an imaging plane. Japanese Patent Laid-Open No. 2009-109965 discloses a structure in which the focal point of a microlens for a focus detection pixel is closer to the microlens than the focal point of a microlens for an image pickup pixel. Japanese Patent Laid-Open No. 2009-290157 discloses a structure in which the position of a microlens for a focus detection pixel and the position of a microlens for an image pickup pixel are varied in accordance with an image height.
Japanese Patent Laid-Open No. 2009-086144 discloses a structure in which pixels forming a set of pixels are provided with respective microlenses of different shapes. Then, focus detection is performed by comparing the outputs from these pixels.
Japanese Patent Laid-Open Nos. 2009-109965 and 2009-290157 each state that focus detection accuracy can be improved in the image pickup device which includes focus detection pixels and image pickup pixels provided in the imaging plane. However, no sufficient studies have been done to improve both focus detection accuracy based on phase difference detection and image pickup performance. The term “image pickup performance” refers to, for example, sensitivity to oblique incident light, or capability to reduce mixing of colors derived from adjacent pixel signals of different colors. Japanese Patent Laid-Open No. 2009-086144 states that it is possible to eliminate the need of an optical path splitting unit. However, again, no sufficient studies have been done to improve both focus detection accuracy and image pickup performance.